Beach dipping (like pond dipping but saltier)

This week we headed down to the beach after the hubster finished work. The tide was going out, but not enough to expose the (fairly poor) rock pools we have locally, so the boys turned their attention to the sea itself to look for beasties. We equipped the boys with nets and showed them how to swish them through the water and investigate the contents. I christened the activity ‘beach dipping’ because it was more like pond dipping than fishing. I was expecting the kids to catch a few shrimp, but what they came up with was far more exciting.

“What are these weird blobs?” they asked. What they had caught were ctenophores, aka comb jellies, aka sea gooseberries, Ctenophore is from the Greek for ‘comb bearer’, referring to the lines of cilia – hair-thin protuberances which the comb jelly wiggles to propel itself along. They are the largest creatures to swim by this method. The ones we found were the size of my thumb nail but the largest, appropriately named the giant comb jelly (and featured on an episode of the Octonauts) can grow to 1.5m. They mainly spherical and share a jelly-like consistency with jellyfish, however jellyfish are in a different phylum (they are cnidarians).

Comb jellies

The species of comb jelly we found feed by means of a pair of sticky tentacles. Prey adhere to these, then the jelly spins and whips the food up into it’s mouth. One of the jellies we found had the tiny eyes of it’s recent meal peering out through the jelly’s transparent gut. My favourite feature of comb jellies is their ability to generate a light show as they have bioluminescent cells running along their lengths.

These features of the comb jelly’s form, movement, feeding and bioluminescence are things which I had read about and seen in videos, but had never expected to see being acted out in a pink plastic bucket on Bexhill beach! The boys were as excited as I was to see the faint row of lights rippling along the length of the little blobs as they sped around the bucket, twirling as they noodled their tentacles up to their mouths to feed.

Click here for a link to a video I found online which shows a species of comb jelly that looks very like the one we found, complete with light show and feeding behaviour.

Dog whelks and their eggs

Our exploration of the beach also turned up a nice shore crab, who almost floated into our bucket as he was washed towards the sea by the draining of the beach as the tide rapidly retreated. Toby also spotted more strange blobs, which were the eggs of dog whelks attached to a wooden groyne (the papery ball shaped masses you find blowing around on the beach are a different species of whelk’s eggs). A less savoury but equally interesting find was a deceased dog fish, which in usual kid fashion the boys squatted over and poked with a stick for a while “can we eat it?”, “no,dear”, “whyyyy?”, “well, it smells funny and has chunks missing out of it, shall we not”.

All in all an excellent lesson in intertidal and marine fauna! If you want kids to learn about natural environments, getting them out in nature is vital, and is as easy to do as spending an afternoon with a bucket and a net.

Notes: I have no affiliation to the link provided, it was just a useful video to explain what we saw. Usual safety precautions around small kids and water apply. All beasties caught were returned to the sea within ten minutes. We live in the UK so unpleasant or dangerous things are pretty rare – I’ve seen a ‘by-the-wind-sailor’ (Vellela vellela, a tiny relative of the Portuguese man-o-war) once in all my years of beach walking, and once a box jelly washed up, nothing else remotely stinging. The ‘don’t touch it if you don’t know what it is’ rule is a good thing to teach kids anywhere though. Further down the coast from us there have been reports of weaver fish, which can sting painfully if stood on. It’s always a good idea to check local advice where you live, especially if you are in warmer climes than we are.

15 Comments

Oh my goodness that video is amazing, so pretty and it doesn’t look real. What an incredible find! You should think about writing a guide to the things you can find in rock pools or on the sea shore. I’d find it fascinating and I’m sure lots of others would too.
Nat.x

Goodness what an exciting discovery. I have had a real education reading this and had never heard of comb jellies before. The video is fascinating, how clever these little creatures are and how clever of you to know what they were. I shall have to look out for them at the beach now. We are going tomorrow, I might just back a few nets. Love the beach dipping description too, it describes what you were doing perfectly.